FIG. 1 depicts a diagram of the salient components of wireless telecommunications system 100 in accordance with the prior art. Wireless telecommunications system 100 comprises: wireless terminal 101, base stations 102-1 and 102-2, distributed antenna 103, repeater antenna 104, and wireless switching center 111, interrelated as shown. Wireless telecommunications system 100 provides wireless telecommunications service to all of geographic region 120, in well-known fashion.
Base station 102-1 comprises an antenna that radiates a first signal into geographic region 120. The first signal has a limited range, however, and, therefore, is receivable and decodable in a limited area. To increase the area in which the first signal is receivable and decodable, wireless telecommunications system 100 employs an additional antenna—distributed antenna 103—to also radiate the first signal. Distributed antenna 103 receives the first signal from base station 102-1, via wireline transmission medium 103-3, and also radiates the first signal. From the perspective of wireless terminal 101, the first signal as radiated by base station 102-1 is indistinguishable from the first signal as radiated by distributed antenna 103, and, therefore, by working together, base station 102-1 and distributed antenna 103 increase the area in which the first signal is receivable and decodable.
Base station 102-2 comprises an antenna that radiates a second signal into geographic region 120. The second signal has a limited range, however, and, therefore, is receivable and decodable in a limited area. To increase the area in which the second signal is receivable and decodable, wireless telecommunications system 100 employs an additional antenna—repeater antenna 104—to also radiate the second signal. Repeater antenna 104 receives the second signal from base station 102-2, wirelessly, and “repeats” or re-radiates the second signal. From the perspective of wireless terminal 101, the second signal as radiated by base station 102-2 is indistinguishable from the second signal as radiated by repeater antenna 104, and, therefore, by working together, base station 102-2 and repeater antenna 104 increase the area in which the second signal is receivable and decodable.
Although the details of how distributed antenna 103 and repeater antenna 104 are built and operated are different, their effect is, for the purposes of the present specification, essentially the same as a base station antenna. Each radiates a signal to and for a wireless terminal. For the purposes of this specification, an “infrastructure antenna” is defined as an antenna in a wireless telecommunications system that radiates a signal to and for a wireless terminal.
The salient advantage of wireless telecommunications over wireline telecommunications is the mobility that is afforded to the user of the wireless terminal. On the other hand, the salient disadvantage of wireless telecommunications lies in that fact that because the user is mobile, an interested party might not be able to readily ascertain the location of the user.
Such interested parties might include both the user of the wireless terminal and a remote party. There are a variety of reasons why the user of a wireless terminal might be interested in knowing his or her location. For example, the user might be interested in telling a remote party where he or she is or, alternatively, the user might seek advice in navigation.
In addition, there are a variety of reasons why a remote party might be interested in knowing the location of the user. For example, the recipient of an E 9-1-1 emergency call from a wireless terminal might be interested in knowing the location of the wireless terminal so that emergency services vehicles can be dispatched to that location.
There are many techniques in the prior art for estimating the location of a wireless terminal. A number of these techniques need to know which infrastructure antenna radiates the signal that is received and decoded by the wireless terminal. In wireless telecommunications systems without distributed or repeater antennas, this is generally not a problem because each signal is uniquely associated with one infrastructure antenna. Therefore, the decoding and identification of a signal is tantamount to the identification of the infrastructure antenna that radiated it.
In wireless telecommunications systems with distributed and/or repeater antennas, however, the decoding and identification of a signal does not indicate which infrastructure antenna radiated it. Therefore, the need exists for a technique for estimating the location of a wireless terminal in a wireless telecommunications system that comprises distributed and/or repeater antennas.